aarch64: Fix folding of degenerate svwhilele case [PR117045]

The svwhilele folder mishandled the degenerate case in which
the second argument is the maximum integer.  In that case,
the result is all-true regardless of the first parameter:

  If the second scalar operand is equal to the maximum signed integer
  value then a condition which includes an equality test can never fail
  and the result will be an all-true predicate.

This is because the conceptual "increment the first operand
by 1 after each element" is done modulo the range of the operand.
The GCC code was instead treating it as infinite precision.
whilele_5.c even had a test for the incorrect behaviour.

The easiest fix seemed to be to handle that case specially before
doing constant folding.  This also copes with variable first operands.

gcc/
	PR target/116999
	PR target/117045
	* config/aarch64/aarch64-sve-builtins-base.cc
	(svwhilelx_impl::fold): Check for WHILELTs of the minimum value
	and WHILELEs of the maximum value.  Fold them to all-false and
	all-true respectively.

gcc/testsuite/
	PR target/116999
	PR target/117045
	* gcc.target/aarch64/sve/acle/general/whilele_5.c: Fix bogus
	expected result.
	* gcc.target/aarch64/sve/acle/general/whilele_11.c: New test.
	* gcc.target/aarch64/sve/acle/general/whilele_12.c: Likewise.

gcc/config/aarch64/aarch64-sve-builtins-base.cc

@@ -2945,7 +2945,9 @@ public:
     : while_comparison (unspec_for_sint, unspec_for_uint), m_eq_p (eq_p)
   {}
 
-  /* Try to fold a call by treating its arguments as constants of type T.  */
+  /* Try to fold a call by treating its arguments as constants of type T.
+     We have already filtered out the degenerate cases of X .LT. MIN
+     and X .LE. MAX.  */
   template<typename T>
   gimple *
   fold_type (gimple_folder &f) const
@@ -3001,6 +3003,13 @@ public:
     if (f.vectors_per_tuple () > 1)
       return nullptr;
 
+    /* Filter out cases where the condition is always true or always false.  */
+    tree arg1 = gimple_call_arg (f.call, 1);
+    if (!m_eq_p && operand_equal_p (arg1, TYPE_MIN_VALUE (TREE_TYPE (arg1))))
+      return f.fold_to_pfalse ();
+    if (m_eq_p && operand_equal_p (arg1, TYPE_MAX_VALUE (TREE_TYPE (arg1))))
+      return f.fold_to_ptrue ();
+
     if (f.type_suffix (1).unsigned_p)
       return fold_type<poly_uint64> (f);
     else

gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_11.c

@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#include <arm_sve.h>
+#include <limits.h>
+
+svbool_t
+f1 (volatile int32_t *ptr)
+{
+  return svwhilelt_b8_s32 (*ptr, INT32_MIN);
+}
+
+svbool_t
+f2 (volatile uint32_t *ptr)
+{
+  return svwhilelt_b16_u32 (*ptr, 0);
+}
+
+svbool_t
+f3 (volatile int64_t *ptr)
+{
+  return svwhilelt_b32_s64 (*ptr, INT64_MIN);
+}
+
+svbool_t
+f4 (volatile uint64_t *ptr)
+{
+  return svwhilelt_b64_u64 (*ptr, 0);
+}
+
+/* { dg-final { scan-assembler-times {\tpfalse\tp[0-9]+\.b\n} 4 } } */

gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_12.c

@@ -0,0 +1,34 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#include <arm_sve.h>
+#include <limits.h>
+
+svbool_t
+f1 (volatile int32_t *ptr)
+{
+  return svwhilele_b8_s32 (*ptr, INT32_MAX);
+}
+
+svbool_t
+f2 (volatile uint32_t *ptr)
+{
+  return svwhilele_b16_u32 (*ptr, UINT32_MAX);
+}
+
+svbool_t
+f3 (volatile int64_t *ptr)
+{
+  return svwhilele_b32_s64 (*ptr, INT64_MAX);
+}
+
+svbool_t
+f4 (volatile uint64_t *ptr)
+{
+  return svwhilele_b64_u64 (*ptr, UINT64_MAX);
+}
+
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.b(?:, all)\n} } } */
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.h(?:, all)\n} } } */
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.s(?:, all)\n} } } */
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.d(?:, all)\n} } } */

gcc/testsuite/gcc.target/aarch64/sve/acle/general/whilele_5.c

@@ -28,7 +28,7 @@ test3 (svbool_t *ptr)
   *ptr = svwhilele_b16_s32 (0x7ffffffb, 0x7fffffff);
 }
 
-/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.h, vl5\n} } } */
+/* { dg-final { scan-assembler {\tptrue\tp[0-9]+\.h(?:, all)\n} } } */
 
 void
 test4 (svbool_t *ptr)